^abManber, Ubi (2007-12-13). "Encouraging people to contribute knowledge". Google. "Earlier this week, we started inviting a selected group of people to try a new, free tool that we are calling "knol", which stands for a unit of knowledge. Our goal is to encourage people who know a particular subject to write an authoritative article about it."

^"Google debuts knowledge project". BBC. 2007-12-15. Diakses 2007-12-15. "Many experts see the initiative as an attack on the widely used Wikipedia communal encyclopaedia."

^"Knol has been discontinued as of May 1, 2012". Google knol. 2012-04-30. Diakses 2013-05-13. "Knol has been discontinued as a service, but we've worked with Solvitor and Crowd Favorite to create Annotum, an open-source platform based upon WordPress that allows you to continue authoring and publishing scholarly articles. To learn more about this announcement, see our Frequently Asked Questions. ."